I'm afraid this step is so straightforward I can't quite see what the concern might be?
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Stephen M. Smith, Professor of Biomedical Engineering
Associate Director, Oxford University FMRIB Centre
FMRIB, JR Hospital, Headington,
Oxford. OX3 9 DU, UK
+44 (0) 1865 222726 (fax 222717)
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http://www.fmrib.ox.ac.uk/~steve
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On 28 Nov 2011, at 10:19, Dan Shaw <[log in to unmask]> wrote:
> Dear all,
>
> As stated in the FSL support material, in a recent manuscript I cited fully FSL and stated that "grand-mean intensity normalisation of the entire 4D dataset by a single multiplicative factor" was carried out.
>
> I didn't think much of this at the time - I understand grand-mean scaling to account for slow-frequency signal changes related to scanner drifts - but one of the reviewers rightly questioned how a single value can be used to normalise ALL the volumes within a time-series.
>
> I have been unable to find any related posts about this, so I suspect that I'm overlooking something fairly simple. But if someone could show me exactly what I'm missing I'd be very grateful.
>
> Many thanks in advance,
>
> Dan.
>
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